Defeated presidential candidate Sean Gallagher has accused RTE of manufacturing live TV drama after a watchdog found the broadcaster aired a tweet from a bogus account without checking its source.

The Frontline, hosted by Pat Kenny, was found to have acted unfairly during the October 24 election debate and made no attempt to verify social media posts.

The Broadcasting Authority of Ireland (BAI) upheld a complaint by the former Dragon's Den investor and Fianna Fail fundraiser, but decided it was not serious enough to warrant an investigation or public hearing.

Mr Gallagher said the ruling confirmed his view there had been an institutional failure by RTE.

"It would appear that the desire to manufacture on-air drama won out over the truth and the production team seemed to have regrettably abandoned RTE's own published standards and guidelines," he said.

Mr Gallagher had been frontrunner in the election race until a story about links to a 5,000 euro political donation for Fianna Fail were revealed on air by Sinn Fein candidate Martin McGuinness.

Mr Kenny then read the tweet: "The man that Gallagher took the cheque from will be at a press conference tomorrow", and incorrectly attributed it to the official Martin McGuiness for President campaign.

Mr Gallagher claimed the Frontline debate was crucial as it was the final head-to-head broadcast in the presidential campaign and less than five days from polling.

In its ruling, the BAI said the attribution of the tweet to the official campaign of Martin McGuiness was incorrect.

RTE has apologised to Mr Gallagher and acknowledged mistakes - described as a communications breakdown in the editorial line of backroom staff.